A novel genetic method "Mapping by Admixture Linkage Disequilibrium" (MALD) has been proposed and implemented which provides a population- and patient cohort-based approach for disease gene identification. The method uses genetic markers with significant allele frequency differences between racial groups and a population with a recent history of admixture to identify novel disease genes in patient cohorts. This methodology is particularly appropriate for diseases where collecting large families for linkage analysis is difficult or where disease onset involves exposure to a common environmental or infectious agent. We have been collecting samples from African American patients for Hepatitis C virus (HCV) clearance, HIV-1/AIDS, focal segmental glomerulosclerosis, end-stage renal disease and prostate cancer. The projects are currently ongoing with MALD mapping genotypes collected from 1929 patients totally 4,901,589 genotypings for 2541 loci. Analysis of this data and the diseases of Hepatitis C virus (HCV) clearance, HIV-1/AIDS, focal segmental glomerulosclerosis is ongoing utilizing the ANCESTRYMAP program we described.